The present invention generally relates to combustion apparatus and, in a preferred embodiment thereof, more particularly relates to a specially designed dual fuel burner system for a fuel-fired heating appliance such as, for example, a boiler.
Dual fuel boilers have been supplied, primarily by power burner type boiler manufacturers, for many years. The ability to selectively operate a boiler, or other type of fuel-fired heating appliance, with one or the other of two different fuels (such as, for example, natural gas or propane) is desirable to provide operation if and when the primary fuel source is interrupted. Often the pricing of the primary fuel source can be discounted if the customer agrees to accept interruption of the fuel supply by the supplier when so requested. In this event, the customer simply switches to the secondary or “backup” fuel source until the source of primary fuel is re-established by the supplier.
Current power burner practices are (1) to have two separate burner heads that can be interchanged to accommodate the switch back and forth between the two different types of fuel, or (2) to have back-up fuels which essentially the same heating value and Wobbe indexes such as propane-air to back up natural gas. This conventional design, of course, requires a mechanical modification to the overall burner structure each time that a different fuel is to be used to fire the boiler. It would thus be desirable to provide a dual fuel heating appliance, such as a boiler, incorporating therein a simplified technique for switching back and forth between two alternative fuel sources. It is to this goal that the present invention is primarily directed.